As an extender pigment in cosmetics, in general, scaly powders such as talc, mica and sericite have been conventionally used. Particles in the form of scale are suitable for the use in make-up cosmetics because of their good extensibility, namely, slipperiness on skin and very pleasant feeling at use.
However, since these powders are obtained by crushing natural minerals, they have a color of grey or brown due to impurities present in their lattices. Accordingly, the original scaly powder color disadvantageously remains when the powders are compounded in cosmetics.
Also, since these powders are natural products, it is difficult to secure minerals having stable properties in a sufficiently enough amount and in particular, sericite has become hardly available. Mica can be procured relatively easily; however, because of its cleavage property, the mica cannot keep the form of scaly powder stably as a matter of defect.
Accordingly, techniques have been proposed for applying to cosmetics scaly powders of barium sulfate which is easily chemically synthesized.
JP-B-62-34688 (the term "JP-B" as used herein means an "examined Japanese patent publication") discloses a process for producing plate barium sulfates having a uniform particle size by reacting barium sulfide with sulfuric acid at a molar ratio of 1:1. However, according to this method, the barium sulfates are obtained in the form of a coarse particle. Although they may be suitable for the application to additives for synthetic resins or the like, the use in cosmetics cannot always be satisfied.
JP-A-3-257016 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a process for producing plate barium sulfates having an aspect ratio of from 5 to 100 and a ratio of the square of the peripheral length to the area of the orthogonal projection face of the plate surface of from 20:1 to 150:1 by reacting a soluble barium salt with a sulfate. This process relates to plate barium sulfates for use in cosmetics having excellent use feeling and transparency but is accompanied by a doubt of deleteriousness to a human body, in particular, the skin. Also, the resulting plate barium sulfates cannot satisfy the slipperiness as a requirement for cosmetics.
JP-A-6-92630 discloses a process for producing plate barium sulfates having a narrow particle size distribution and excellent optical properties by adding a slight amount of sparingly soluble fine crystals to react with a soluble barium salt and a sulfate. However, in this technique, no investigation is made on the deleteriousness to the skin. Although the transparency can be achieved, the touch, the feel and the like as properties required for cosmetics are not examined.